1. Field of the Invention
The present invention relates to an apparatus for non-invasively monitoring at least electrocardiograms and blood pressures, the electrocardiograms being led from an electrocardiogram electrode and the blood pressure being output from a non-invasive blood-pressure measuring apparatus (NIBP).
2. Related Art
The non-invasive patient monitoring apparatus monitors mainly electrocardiograms, arterial oxygen saturation and blood pressure (measured by the NIBP) as parameters representing dynamic states of circulation of a patient. The patient monitoring apparatus periodically measures a blood pressure by the NIBP. When the blood pressure abruptly changes during the interval between the adjacent measurements, the patient monitoring apparatus will miss the measurement of the abrupt change of blood pressure. To avoid the missing of the measurement, the heart rate, which is relatively sensitive to changes in the status of cardiovascular circulation, is used for its parameter monitoring. If the heart rate being monitored varies out of a preset range of its values, the patient monitoring apparatus generates an alarm. The operator recognizes the generated alarm and operates the non-invasive blood-pressure measuring apparatus to measure a blood pressure of the patient.
In a case where a patient suffering from a sinus arrhythmia at an acute stage, and an external or implantable pacemaker is attached to him in the ICU, ward or operating room, it is necessary to carefully monitor his blood pressure because the following situations will take place.
(1) When the ventricle is paced by use of a pacemaker, the cardiac output sometimes decreases even if at the same heart rate. This fact is known. When the ventricle of the heart is paced, and a dynamic state of the heart shifts from a sinus rhythm contraction (which is attendant with an autonomic contraction of the atrium) to a ventricular contraction, the heart exhibits an electrocardiogram as shown in FIG. 16(a). Inthiscase,thecardiac output decreases to about 80% of that in a normal state, and the blood pressure also decreases as shown in FIG. 16(b).
(2) There is a case where when the patient is paced for a long time, a stimulus threshold value of the myocardium abnormally increases, and the same phenomenon likewise takes place depending on some kinds of medicines prescribed. In this case, the pacing is imcompetence in spite of pacing to recover from the bradycardia, as shown in FIG. 17(a). At this time, it is estimated that a blood pressure of the arteria decreases as shown in FIG. 17(b).
As described above, there is a case where a blood pressure descending state remains unchanged even if the heart is paced with the pacemaker. Therefore, it is very important to measure a blood pressure of the patient with the pacemaker attached. For those reasons, the patient monitoring apparatus, by convention, detects an abrupt change of blood pressure through the monitoring of heat rates, and generates an alarm. The operator recognizes the alarm and manually operates the NIBP to measure a blood pressure of the patient attached with pacemaker.
An optimum range of heart rates set for generating an alarm is different for each patient, and therefore its setting is complicated. When a bradycardia occurs in the patient, the pacing of the heart is immediately started. Therefore, the heat-rate basis alarm is not always generated.
For the patient attached with a pacemaker, an immediate monitoring of his blood pressure is essential when a bradycardia occurs. In this case, the operator drives the NIBP by manual after the alarm generation, and this makes it difficult for the operator to quickly start the blood pressure measurement.